[FFI][REFACTOR] Refactor AccessPath to enable full tree repr

ffi/CMakeLists.txt

@@ -59,7 +59,6 @@ set(tvm_ffi_objs_sources
   "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/dtype.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/testing.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/container.cc"
-  "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/reflection/access_path.cc"
 )
 
 if (TVM_FFI_USE_EXTRA_CXX_API)
@@ -69,6 +68,7 @@ if (TVM_FFI_USE_EXTRA_CXX_API)
     "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/extra/json_parser.cc"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/extra/json_writer.cc"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/extra/serialization.cc"
+    "${CMAKE_CURRENT_SOURCE_DIR}/src/ffi/extra/reflection_extra.cc"
   )
 endif()
 

ffi/include/tvm/ffi/c_api.h

@@ -896,7 +896,7 @@ TVM_FFI_DLL const TVMFFITypeInfo* TVMFFIGetTypeInfo(int32_t type_index);
 #endif
 
 //---------------------------------------------------------------
-// The following API defines static object field accessors
+// The following API defines static object attribute accessors
 // for language bindings.
 //
 // They are defined in C++ inline functions for cleaner code.

ffi/include/tvm/ffi/reflection/access_path.h

@@ -25,24 +25,31 @@
 
 #include <tvm/ffi/any.h>
 #include <tvm/ffi/c_api.h>
+#include <tvm/ffi/cast.h>
 #include <tvm/ffi/container/array.h>
 #include <tvm/ffi/container/tuple.h>
+#include <tvm/ffi/error.h>
 #include <tvm/ffi/reflection/registry.h>
 
+#include <vector>
+
 namespace tvm {
 namespace ffi {
 namespace reflection {
 
 enum class AccessKind : int32_t {
-  kObjectField = 0,
+  kAttr = 0,
   kArrayItem = 1,
   kMapItem = 2,
   // the following two are used for error reporting when
   // the supposed access field is not available
-  kArrayItemMissing = 3,
-  kMapItemMissing = 4,
+  kAttrMissing = 3,
+  kArrayItemMissing = 4,
+  kMapItemMissing = 5,
 };
 
+class AccessStep;
+
 /*!
  * \brief Represent a single step in object field, map key, array index access.
  */
@@ -59,16 +66,18 @@ class AccessStepObj : public Object {
    */
   Any key;
 
+  // default constructor to enable auto-serialization
+  AccessStepObj() = default;
   AccessStepObj(AccessKind kind, Any key) : kind(kind), key(key) {}
 
-  static void RegisterReflection() {
-    namespace refl = tvm::ffi::reflection;
-    refl::ObjectDef<AccessStepObj>()
-        .def_ro("kind", &AccessStepObj::kind)
-        .def_ro("key", &AccessStepObj::key);
-  }
+  /*!
+   * \brief Deep check if two steps are equal.
+   * \param other The other step to compare with.
+   * \return True if the two steps are equal, false otherwise.
+   */
+  inline bool StepEqual(const AccessStep& other) const;
 
-  static constexpr const char* _type_key = "tvm.ffi.reflection.AccessStep";
+  static constexpr const char* _type_key = "ffi.reflection.AccessStep";
   static constexpr TVMFFISEqHashKind _type_s_eq_hash_kind = kTVMFFISEqHashKindConstTreeNode;
   TVM_FFI_DECLARE_FINAL_OBJECT_INFO(AccessStepObj, Object);
 };
@@ -82,8 +91,10 @@ class AccessStep : public ObjectRef {
  public:
   AccessStep(AccessKind kind, Any key) : ObjectRef(make_object<AccessStepObj>(kind, key)) {}
 
-  static AccessStep ObjectField(String field_name) {
-    return AccessStep(AccessKind::kObjectField, field_name);
+  static AccessStep Attr(String field_name) { return AccessStep(AccessKind::kAttr, field_name); }
+
+  static AccessStep AttrMissing(String field_name) {
+    return AccessStep(AccessKind::kAttrMissing, field_name);
   }
 
   static AccessStep ArrayItem(int64_t index) { return AccessStep(AccessKind::kArrayItem, index); }
@@ -94,15 +105,273 @@ class AccessStep : public ObjectRef {
 
   static AccessStep MapItem(Any key) { return AccessStep(AccessKind::kMapItem, key); }
 
-  static AccessStep MapItemMissing(Any key) { return AccessStep(AccessKind::kMapItemMissing, key); }
+  static AccessStep MapItemMissing(Any key = nullptr) {
+    return AccessStep(AccessKind::kMapItemMissing, key);
+  }
 
   TVM_FFI_DEFINE_NOTNULLABLE_OBJECT_REF_METHODS(AccessStep, ObjectRef, AccessStepObj);
 };
 
-using AccessPath = Array<AccessStep>;
+inline bool AccessStepObj::StepEqual(const AccessStep& other) const {
+  return this->kind == other->kind && AnyEqual()(this->key, other->key);
+}
+
+// forward declaration
+class AccessPath;
+
+/*!
+ * \brief ObjectRef class of AccessPathObj.
+ *
+ * \sa AccessPathObj
+ */
+class AccessPathObj : public Object {
+ public:
+  /*!
+   * \brief The parent of the access path.
+   *
+   * This parent-pointing tree structure is more space efficient when
+   * representing multiple paths that share a common prefix.
+   *
+   * \note Empty for root.
+   */
+  Optional<ObjectRef> parent;
+  /*!
+   * \brief The current of the access path.
+   * \note Empty for root.
+   */
+  Optional<AccessStep> step;
+  /*!
+   * \brief The current depth of the access path, 0 for root
+   */
+  int32_t depth;
+
+  // default constructor to enable auto-serialization
+  AccessPathObj() = default;
+  /*!
+   * \brief Constructor for the access path.
+   * \param parent The parent of the access path.
+   * \param step The current step of the access path.
+   * \param depth The current depth of the access path.
+   */
+  AccessPathObj(Optional<ObjectRef> parent, Optional<AccessStep> step, int32_t depth)
+      : parent(parent), step(step), depth(depth) {}
+
+  /*!
+   * \brief Get the parent of the access path.
+   * \return The parent of the access path.
+   */
+  inline Optional<AccessPath> GetParent() const;
+
+  /*!
+   * \brief Extend the access path with a new step.
+   * \param step The step to extend the access path with.
+   * \return The extended access path.
+   */
+  inline AccessPath Extend(AccessStep step) const;
+
+  /*!
+   * \brief Extend the access path with an object attribute access.
+   * \param field_name The name of the field to access.
+   * \return The extended access path.
+   */
+  inline AccessPath Attr(String field_name) const;
+
+  /*!
+   * \brief Extend the access path with an object attribute missing access.
+   * \param field_name The name of the field to access.
+   * \return The extended access path.
+   */
+  inline AccessPath AttrMissing(String field_name) const;
+
+  /*!
+   * \brief Extend the access path with an array item access.
+   * \param index The index of the array item to access.
+   * \return The extended access path.
+   */
+  inline AccessPath ArrayItem(int64_t index) const;
+
+  /*!
+   * \brief Extend the access path with an array item missing access.
+   * \param index The index of the array item to access.
+   * \return The extended access path.
+   */
+  inline AccessPath ArrayItemMissing(int64_t index) const;
+
+  /*!
+   * \brief Extend the access path with a map item access.
+   * \param key The key of the map item to access.
+   * \return The extended access path.
+   */
+  inline AccessPath MapItem(Any key) const;
+
+  /*!
+   * \brief Extend the access path with a map item missing access.
+   * \param key The key of the map item to access.
+   * \return The extended access path.
+   */
+  inline AccessPath MapItemMissing(Any key) const;
+
+  /*!
+   * \brief Get the array of steps that corresponds to the access path.
+   * \return The array of steps that corresponds to the access path.
+   */
+  inline Array<AccessStep> ToSteps() const;
+
+  /*!
+   * \brief Check if two paths are equal by deep comparing the steps.
+   * \param other The other path to compare with.
+   * \return True if the two paths are equal, false otherwise.
+   */
+  inline bool PathEqual(const AccessPath& other) const;
+
+  /*!
+   * \brief Check if this path is a prefix of another path.
+   * \param other The other path to compare with.
+   * \return True if this path is a prefix of the other path, false otherwise.
+   */
+  inline bool IsPrefixOf(const AccessPath& other) const;
+
+  static constexpr const char* _type_key = "ffi.reflection.AccessPath";
+  static constexpr TVMFFISEqHashKind _type_s_eq_hash_kind = kTVMFFISEqHashKindConstTreeNode;
+  TVM_FFI_DECLARE_FINAL_OBJECT_INFO(AccessPathObj, Object);
+
+ private:
+  static bool PathEqual(const AccessPathObj* lhs, const AccessPathObj* rhs) {
+    // fast path for same pointer
+    if (lhs == rhs) return true;
+    if (lhs->depth != rhs->depth) return false;
+    // do deep equality checks
+    while (lhs->parent.has_value()) {
+      TVM_FFI_ICHECK(rhs->parent.has_value());
+      TVM_FFI_ICHECK(lhs->step.has_value());
+      TVM_FFI_ICHECK(rhs->step.has_value());
+      if (!(*lhs->step)->StepEqual(*(rhs->step))) {
+        return false;
+      }
+      lhs = static_cast<const AccessPathObj*>(lhs->parent.get());
+      rhs = static_cast<const AccessPathObj*>(rhs->parent.get());
+      // fast path for same pointer
+      if (lhs == rhs) return true;
+      TVM_FFI_ICHECK(lhs != nullptr);
+      TVM_FFI_ICHECK(rhs != nullptr);
+    }
+    return true;
+  }
+};
+
+/*!
+ * \brief ObjectRef class of AccessPath.
+ *
+ * \sa AccessPathObj
+ */
+class AccessPath : public ObjectRef {
+ public:
+  /*!
+   * \brief Create an access path from an iterator range of steps.
+   * \param begin The beginning of the iterator range.
+   * \param end The end of the iterator range.
+   * \return The access path.
+   */
+  template <typename Iter>
+  static AccessPath FromSteps(Iter begin, Iter end) {
+    AccessPath path = AccessPath::Root();
+    for (Iter it = begin; it != end; ++it) {
+      path = path->Extend(*it);
+    }
+    return path;
+  }
+  /*!
+   * \brief Create an access path from an array of steps.
+   * \param steps The array of steps.
+   * \return The access path.
+   */
+  static AccessPath FromSteps(Array<AccessStep> steps) {
+    AccessPath path = AccessPath::Root();
+    for (AccessStep step : steps) {
+      path = path->Extend(step);
+    }
+    return path;
+  }
+
+  /*!
+   * \brief Create a root access path.
+   * \return The root access path.
+   */
+  static AccessPath Root() {
+    return AccessPath(make_object<AccessPathObj>(std::nullopt, std::nullopt, 0));
+  }
+
+  TVM_FFI_DEFINE_NOTNULLABLE_OBJECT_REF_METHODS(AccessPath, ObjectRef, AccessPathObj);
+};
+
 using AccessPathPair = Tuple<AccessPath, AccessPath>;
 
+inline Optional<AccessPath> AccessPathObj::GetParent() const {
+  if (auto opt_parent = this->parent.as<AccessPath>()) {
+    return opt_parent;
+  }
+  return std::nullopt;
+}
+
+inline AccessPath AccessPathObj::Extend(AccessStep step) const {
+  return AccessPath(make_object<AccessPathObj>(GetRef<AccessPath>(this), step, this->depth + 1));
+}
+
+inline AccessPath AccessPathObj::Attr(String field_name) const {
+  return this->Extend(AccessStep::Attr(field_name));
+}
+
+inline AccessPath AccessPathObj::AttrMissing(String field_name) const {
+  return this->Extend(AccessStep::AttrMissing(field_name));
+}
+
+inline AccessPath AccessPathObj::ArrayItem(int64_t index) const {
+  return this->Extend(AccessStep::ArrayItem(index));
+}
+
+inline AccessPath AccessPathObj::ArrayItemMissing(int64_t index) const {
+  return this->Extend(AccessStep::ArrayItemMissing(index));
+}
+
+inline AccessPath AccessPathObj::MapItem(Any key) const {
+  return this->Extend(AccessStep::MapItem(key));
+}
+
+inline AccessPath AccessPathObj::MapItemMissing(Any key) const {
+  return this->Extend(AccessStep::MapItemMissing(key));
+}
+
+inline Array<AccessStep> AccessPathObj::ToSteps() const {
+  std::vector<AccessStep> reverse_steps;
+  reverse_steps.reserve(this->depth);
+  const AccessPathObj* current = this;
+  while (current->parent.has_value()) {
+    TVM_FFI_ICHECK(current->step.has_value());
+    reverse_steps.push_back(*(current->step));
+    current = static_cast<const AccessPathObj*>(current->parent.get());
+    TVM_FFI_ICHECK(current != nullptr);
+  }
+  return Array<AccessStep>(reverse_steps.rbegin(), reverse_steps.rend());
+}
+
+inline bool AccessPathObj::PathEqual(const AccessPath& other) const {
+  return PathEqual(this, other.get());
+}
+
+inline bool AccessPathObj::IsPrefixOf(const AccessPath& other) const {
+  if (this->depth > other->depth) {
+    return false;
+  }
+  const AccessPathObj* rhs_path = other.get();
+  while (rhs_path->depth > this->depth) {
+    TVM_FFI_ICHECK(rhs_path->parent.has_value());
+    rhs_path = static_cast<const AccessPathObj*>(rhs_path->parent.get());
+  }
+  return PathEqual(this, rhs_path);
+}
+
 }  // namespace reflection
 }  // namespace ffi
 }  // namespace tvm
+
 #endif  // TVM_FFI_REFLECTION_ACCESS_PATH_H_